Hallelujah. ("Small favors.") All this past week there's been a plumber truck in front of the building. Obviously when there are fluctuations in the water pressure, it affects the function of the toilets, etc. That's a big issue in this building. And they just got a new pump.
Around the time they installed the new pump, the pressure blew out the refrigerator water line and also the water heater connection, which caused serious flooding. (My neighbor was up to her knees in water.) I'd bought a new water heater last fall and had it installed by a professional plumber. Meanwhile the maintenance people in this building, who are not professional plumbers, have been tinkering with the water pressure and causing all kinds of problems.